Generally, a fuel cell system may include a fuel cell stack, and a fuel supply part for supplying fuel containing hydrogen to the fuel cell stack and an air supply part for supplying an oxidant containing oxygen necessary for an electrochemical reaction of the fuel cell stack. The fuel cell system having the above structure generates electrical energy by the electrochemical reaction between fuel and air, and discharges heat and water as by-products of the reaction.
The fuel cell stack is formed by successively arranging the separating plates, where the separating plates may be each disposed on both sides of a membrane-electrode assembly (MEA) with the membrane-electrode assembly interposed.
The separating plate may include a pair of metal plates, and the separating plate is provided with a hydrogen passage and an air passage for supplying fuel and air to the membrane-electrode assembly, respectively, and a coolant passage for allowing a cooling medium (for example, cooling water) to flow. At this time, the coolant passage may be provided so that the cooling medium flows into the space between the pair of plates.
On the other hand, as the coolant passage is dependently formed for the hydrogen passage (anode passage) and the air passage (cathode passage), the conventionally stamping-molded metal separating plate has a problem that it is difficult to uniformly supply the cooling water over the reaction surface due to the design limitation. Particularly, when the cooling water is not uniformly supplied over the reaction surface, there is a problem that the temperature control of the reaction surface becomes non-uniform and the performance and durability of the fuel cell deteriorate.